A code to model permeation behavior of hydrogen isotopes through bcc Fe was developed by means of a Monte Carlo technique. This code enables correlation of atomic-scale information such as diffusion barrier or adsorption energy with macroscopic quantities such as solubility or permeability. Model parameters were derived from results of ab initio calculations in density function theory. To validate the code, both temperaturedependent permeability and pressure-dependent solubility for hydrogen were evaluated. Simulation results provided reasonable permeability and solubility compared with experimental data, and adequately showed their temperature/pressure dependence.